66565440 has 168 divisors, whose sum is σ = 237149640. Its totient is φ = 17117184.

The previous prime is 66565439. The next prime is 66565453. The reversal of 66565440 is 4456566.

It is a happy number.

66565440 is a `hidden beast` number, since 66 + 56 + 544 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 6843456 + 59721984 = 2616^2 + 7728^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 66565395 and 66565404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 83122 + ... + 83918.

It is an arithmetic number, because the mean of its divisors is an integer number (1411605).

Almost surely, 2^66565440 is an apocalyptic number.

66565440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66565440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118574820).

66565440 is an abundant number, since it is smaller than the sum of its proper divisors (170584200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66565440 is a wasteful number, since it uses less digits than its factorization.

66565440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 849 (or 836 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 36.

The square root of 66565440 is about 8158.7646123663. The cubic root of 66565440 is about 405.2748020669.

The spelling of 66565440 in words is "sixty-six million, five hundred sixty-five thousand, four hundred forty".